The present invention relates to an improved apparatus and process for the extrusion of a rod-like coal-containing body.
Extrusion apparatus and processes for the preparation of a cohesive, continuous, rod-like body from a coal-containing particulate mixture are well-known in the art. One type of such apparatus includes an extruder screw disposed within an extruder barrel. Means (e.g. a feed hopper) connected to the barrel are provided for feeding a mixture containing powdered or finely divided coal and a binder therefor into the barrel at an upstream location thereof. Die means are connected to a discharge or downstream portion of the barrel for receiving and shaping the mixture forcibly discharged from the barrel portion. Means (e.g. a motor-driven shaft) are operatively associated with the screw for driving it. For some applications, means are provided adjacent the barrel for heating at least a portion thereof. This type of apparatus may further include means positioned downstream of the die means for severing the emerging rod-like body.
In a related process for the extrusion of a rod-like coal-containing body of the above-described type, the feed mixture is fed into the barrel adjacent one end thereof. The mixture is moved through the barrel by the rotation of the extruder screw and is forcibly discharged from the downstream end thereof through the die means.
Apparatus generally of the foregoing type is described by Furman in U.S. Pat. Nos. 4,025,262 and 4,049,392. In those patents, control means are disclosed for adjusting the length of the consolidating coal-containing mixture in contact with the surface of the die in response to selected parameters. The die means is of substantially constant or uniform cylindrical configuration and provision is made for relative movement between the die means and the screw. In Furman, U.S. Pat. Nos. 3,989,433 and 4,049,390, there is described apparatus of the foregoing type, which further includes movable die wall portions (e.g. pivotally mounted elements) referred to therein as "flappers" for automatically controlling the throughput resistance experienced by the rod-like body. All of the foregoing patents are incorporated herein by reference.
The inventions described in the above-cited patents are substantial advances in the art. However, there is room for further improvement in coal extrusion apparatus of the above-described type and in coal extrusion processes which may be carried out therein. Such apparatus may be employed in a variety of commercially attractive applications wherein it is desired to extrude the rod-like coal-containing body against high back pressure. In one such application, the extruder apparatus is used for charging a coal gasifier operated at super-atmospheric pressure (e.g. up to 10 atmospheres or more). In such applications the power input required for driving the extruder screw often tends to become undesirably high.
It has been found by practice of the present invention that such advantageous apparatus and process are provided, whereby the requisite power input is reduced for any given extrusion rate. In the present process and apparatus, a lubricant is deposited directly onto the outer surface of the rod-forming mixture as it passes into the die. In this manner, the present invention performs the function of reducing the frictional forces exerted by the wall of the die on the rod-like body being formed therein to effectuate reduced power consumption, a result which eluded heretofore proposed structures and processes wherein lubricant was introduced into the interior of the mixture employed.